A microbial fuel cell (MFC) refers to an apparatus which can directly convert chemical energy of organic matter into electric energy using microbes capable of extracellularly transferring electrons, among anaerobic microbes feeding on organic matter. Particularly, a sediment-type microbial fuel cell can convert chemical energy stored in organic sediment dissolved in water (for example, a sea, a river, a lake) into electric energy using bacteria living in nature, and various research is being conducted to use the sediment-type microbial fuel cell as an apparatus for improving water quality of a body of water including a lake, a waste water treatment plant, and the like or for long-term monitoring of a marine environment.
Generally, a sediment-type microbial fuel cell has a structure in which an anode is placed in sediment and a cathode is placed close to an air space, such that electrons generated upon decomposition of organic matter in the sediment by underwater microbes can be transferred between the electrodes to activate the fuel cell. Such a sediment-type microbial fuel cell can produce electric energy using resources existing in nature and thus is eco-friendly and can be used for a long time without the need for addition of separate organic matter so long as the fuel cell is installed in a body of water containing organic sediment.
However, a typical sediment-type microbial fuel cell has problems in that a mass transfer rate at which organic matter is diffused around electrodes is low due to low molecular diffusion coefficient in sediment, causing a limitation in reduction in power output and current density of the fuel cell, and growth of microbes around the anode is likely to be inhibited due to oxygen crossover from a cathode to an anode caused by layout of the electrodes.